Chatty Cabbies

Who are cab drivers always talking to on their phones? Because they are always, always on the phone. You laugh because you know I'm right.
Let's say any individual cabbie has an 8 hour shift... and let's say it's during the hours of 9-5, when most of the general population is working. At their desks where they can't talk on the phone. Who are they talking to for long periods of time?
And it's not like they are bopping from person to person, no, these are long extensive conversations with the same person.

Or like when I'm in a cab at 2am (not that I ever am grandma, just as a hypothetical), who are they talking to? Maybe other cabbies also working at 2am? Or maybe to family overseas where it's a reasonable hour?

Maybe they're just talking to themselves so as to make their riders think they are popular. I mean, hey, I wouldn't know, because it's never in English. And have you ever noticed that if you have a cab driver who speaks English well... never on the phone. Women? Never on the phone.
In addition to know who they're talking to, I want to know what cell phone plan they have that enables them all those daytime minutes without breaking their wallet. I want on that plan.